1. Field of the Invention
Example embodiments relate to an electrical conductive member (a charging member, a developer earner, a transfer member, or the like) which is provided adjacent to an image carrier, such as a photoconductive drum, a process cartridge including the electrical conductive member and the image carrier formed as at least one unit, and an image forming apparatus such as a copying machine, a printer, a facsimile or the like, which is provided with the electrical conductive member.
2. Description of Related Art
For recent years, in an image forming apparatus of an electrophotographic system such as a copying machine, a printer and a facsimile or the like, a so-called contact-type charging device, which makes a charge roller to contact onto a surface of a photoconductive drum, is commonly used as a charging device which charges equally the surface of the photoconductive drum (the image carrier), instead of a charging apparatus of a corona discharge system.
The contact-type charging device produces smaller amount of ozone and can be charged with a lower voltage in contrast to the charging device of the corona discharge system. However, there have been problems, one is that substance composing a charge roller exudes and adheres onto the surface of a photoconductive drum which abuts with the charge roller, so that the fact of so-called “traces of charge roller” occurs, and other one is that a charge roller abutting with the photoconductive drum vibrates by an application of an alternating voltage, and the fact of so-called “charging noise” is easy to occur in a system of applying the alternating voltage to the charge roller superimposedly.
In addition, as for the contact-type charging device, there have been problems, for examples, one is that a charging ability declines due to residual toner remaining on a surface of a photoconductive drum if the residual toner is transferred to a side of a charge roller after transferring a toner image onto a sheet, and other one is that an abutting portion of a charge roller onto a photoconductive roller has been permanently distorted in a situation after a long-term rest of rotating of a photoconductive drum.
Therefore, to solve the problem described above, a so-called a non-contact type charging device has been proposed, which makes a charge roller to close to a surface of the charge roller and to charge without any contact. (for reference, see JP A 2004-354477).
In a charge roller or a charging member as shown in FIG. 7 of JP A 2004-364477, a electrical resistance adjusting layer 22 is provided on a surface periphery of an electrical conductive supporter 21, which is an axial rod of the charge roller 20, and a set of ring-shaped gap retaining members abutting on both end sides of a photoconductive drum (not shown) are respectively provided on the both sides of the electrical resistance adjusting layer 22, so that a constant gap is retained between the charge roller (the electric resistance adjusting layer) and the photoconductive drum (not shown).
Meantime, as for the conventional charge roller (the charging member) shown in FIG. 7, the gap retaining members 23 are fitted into both end sides of the electrical conductive supporter 21 in such a way of making the ring-shaped gap retaining members 23 to abut with the both sides of the electrical resistance adjusting layer 22 provided on the surface periphery of the electrical conductive supporter.
Therefore, when the gap retaining members 23 are fitted to the both end sides of the electrical conductive supporter 21, if the gap retaining members 23 are in contact with end surfaces of the electrical resistance adjusting layer 22 as pressed thereon, the shapes of the gap retaining members 23 are distorted. Thus, a gap volume provided between the charge roller 20 (the electric resistance adjusting layer) and the photoconductive drum changes dramatically, so that there is a possibility of generating defective conductivity.